This invention relates in general to channel subsystems, and more particularly, to the integration of channel-to-channel functioning into one or more communication channels of a computing environment.
Channel-to-channel adapters have been used for many years as a general purpose communication mechanism between computer systems. For example, channel-to-channel adapters have been the principal mechanism for connecting an S/390 system (offered by International Business Machines Corporation) to other heterogenous environments, such as IBM""s RS/6000 and/or AS/400 systems. The channel-to-channel adapter is protocol independent, and has wide application in areas such as coupling of multiprocessor systems as well as in traditional communications protocol stacks (e.g., TCP/IP, SNA). Conventionally, the CTC function is implemented on a stand-alone piece of hardware.
For parallel channel interfaces, the CTC function is implemented in a separate box outside of, e.g., a Central Electronic Complex (CEC) (offered by International Business Machines Corporation). In IBM Enterprise System Connection Architecture (ESCON), the CTC function is refined so that any particular ESCON channel can be configured as a dedicated channel or a dedicated CTC, through different loads of microcode. For example, reference an IBM publication entitled xe2x80x9cEnterprise Systems Architecture/390 ESCON Channel-To-Channel Adapter,xe2x80x9d Publication No. SA22-7203-00 (1996). In all cases, the xe2x80x9centityxe2x80x9d which provides the CTC function is dedicated to that purpose alone. Unfortunately, significant customer effort and expense is required for CTC configuration using such a dedicated CTC channel approach. Further, if a customer desires CTC communication between two logical partitions (LPARs), at least two channel path IDs (CHPIDs) are required.
In view of the above, a need continues to exist for an enhanced approach to providing CTC functionality within a computing environment to better facilitate communication between computer systems.
To briefly summarize, the present invention comprises in one aspect a method for providing communication between channels of at least one computing environment. The method includes: providing a channel-to-channel (CTC) function integrated within at least one of a first channel and a second channel between which a CTC connection is to be formed; and automatically deciding which of the first channel and the second channel is to provide the CTC function for the CTC connection.
Systems and computer program products corresponding to the above-summarized method are also described and claimed herein.
To restate, provided herein is a technique for implementing channel-to-channel communications within a computing environment that vastly increases a customer""s connectivity options. This is achieved by integrating a channel-to-channel (CTC) function within one or more channels of a computing environment, with each channel also comprising a channel function. Operationally, a work unit is transferred to the CTC function or the channel function based on work unit type, i.e., whether the work unit itself originated with a channel function or a control unit. With the technique of the present invention, any two systems that have at least one channel connected to the network may have CTC connections set up between them with no additional cost. Many of the largest computer users are literally running out of available channel paths, so providing a dedicated CTC function is typically expensive both in terms of consuming scarce channel path ids as well as hardware costs. This is compounded by the fact that typically a customer will require a pair of CTCs for redundancy. However, with the present invention, the customer no longer has to dedicate channel path (CHPID) resources to the CTC function.
Further, the auto-configure feature described herein makes the customer configuration definition for the CTC connection trivial. The customer simply specifies a CTC control unit at at least one end of the connection, and auto-configuration automatically performs load balancing xe2x80x9cunder the coversxe2x80x9d. In addition, an ability to configure logical partition (LPAR)-to-LPAR communication through a single CHPID is provided, which further improves the connectivity options, particularly in low end systems, where the number of available channels may be limited. Although contemplated for Fiber Connection (FICON) channels (FICON channels being offered by International Business Machines Corporation), the concepts presented herein could equally apply to other types of system communication channels.
Additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered part of the claimed invention.